There are a number of medicament delivery devices on the market that are capable of automatically, semi-automatically or manually delivering doses of medicament. Of the known type of delivery devices the “pen-type” injector is gaining in popularity and is available in both reusable and disposable designs. Such devices are constructed with dose setting mechanisms that include a variety of inter-acting components for obtaining desired functions, such as setting a dose and then delivering the set dose. In most cases, these medicament delivery devices have only one or two single fixed dose setting or variable dose setting where each possible set dose must be a multiple of the lowest possible set dose. In other words, these existing variable dose injection devices do not allow a dose to be set that is a fraction of the lowest possible dose
The types of pen-type injector designs have a dose setting mechanism located at the distal end of the device and a medicament container, such as, a cartridge, located in the proximal end. The known injector designs typically are multiple (variable) dose devices, meaning that the user can select (dial) a dose between 0 and a maximum allowable settable dose. A dose dial sleeve is printed with a range of possible dose settings that typically correspond to each possible incremental dose setting. For example, if the injector is designed and manufactured with a maximum dose setting of 80 international units (IU), then each incremental settable dose differs by one IU. Stated differently, to set a dose of 60 IU, the user would rotate a dose setting knob through 60 possible dose settings while viewing the dose dial sleeve marking indicating each incremental dose until it showed 60 IU. Of course, there would be nothing to prevent a user from accidentally setting an under dose of 59 IU or an over dose of 61 IU, especially if the user is physically impaired, for example having reduced eyesight or severe arthritis.
As stated, some injection devices are manufactured and designed as so-called fixed dose designs where the dose dial sleeve contains printing signifying only one or two doses. The design idea behind these devices is for the user is to rotate the dose setting knob until one of the fixed dose settings is observed, typically in a window of the injector housing. However, in such injector designs the user is still required to step through individual equal incremental dose settings until the indicia of the fixed dose setting is observed in the window. Because the dose setting mechanism requires the user to physically step through each incremental dose setting there is nothing to prevent the user from stopping at a dose less than or greater than the fixed dose setting. In addition, the user will experience a haptic or audible notification as the dose setting mechanism is dialed through each incremental dose to arrive at the final dose setting.
Another drawback of the existing injector designs is the inability to have fixed doses that are not multiples of a single incremental value. In other words, if an injector is designed with a maximum settable dose of 80 IU, then typically each incremental dose would be 1 IU. As such, it would not be possible to set a dose of 2.3 IU. The user could only set a dose of 2 or 3 IU. Stated another way, fractional doses could not be set with such a dose setting mechanism. The ability to set fractional doses is important, especially during studies trying to determine optimum dose amounts for newly developed medicaments and/or for new patients using existing medicaments for the first time.
Although there exist many drug delivery devices available for patient use, there is clearly a need to have an injector available that can deliver one or more predetermined fixed doses where at least one of the predetermined fixed doses is a fractional amount of a second predetermined fixed dose. The availability of a pen-type injector where the user cannot set and/or deliver a dose that is not one of a number of predetermined fixed doses is also an important goal. And, it is highly desirable to have an injector design where only a single mechanical component of the dose setting mechanism needs to be redesigned and manufactured in order to change or vary the predetermined fix doses. This would allow cost effective manufacturing of injection devices that could be easily customized for patients to allow the injection of one or more effective doses of medicament specifically tailored to the particular user.
The disclosure presented below solves the above-mentioned problems with existing medicament delivery devices and provides an injector design that fulfills the needs and requirements mentioned above.